For me, my biggest time waster is the Internet. I'll go online to check just one thing, and before I know it, an hour (or two) has passed. I've alloted myself three hours of internet time each day. To some, this is a lot, and to others, not very much, but in addition to teaching several online classes, I am also finishing my DBA online. I also like my social networking very much. To keep myself from sitting and using all three hours at once, I divide my time into 6-30 minute increments, and set the timer on my microwave to keep me on track.
It generally goes something like this:
7 am: email, online courses, FB, Twitter
11 am: research for DBA
2:30 pm: blogging, FB, email
5:00 pm: online courses
7:00 pm: email, research
9:00 pm: FB, Twitter, DBA
Knowing what I'm doing when each time I'm online works for me!